Process for the production of dimethyl 1-methyl-2-(methylcarbamoyl) vinyl phosphate

ABSTRACT

Improved production of dimethyl 1-methyl-2(methylcarbamoyl)vinyl phosphate by the reaction of 2-chloro-Nmethylacetoacetamide with trimethyl phosphite, results from conducting the reaction in the presence of a poly-halogenated lower alkane.

United States Patent Gaertner 1 Oct. 17, 1972 [54] PROCESS FOR THEPRODUCTION OF 3,802,855 8/1957 Whetstone et al. ....260/969 X DIMETHYLl-METHYL-Z- 3,014,838 12/1961 Stiles et al ..260/969 X (METHYLCARBAMOYL)VINYL 3,053,877 9/1962 Birum et al. ..260/969 PHOSPHATE 2,908,60510/1959 Beriger et al. ..260/943 X [72] Inventor: George W. Gaertner,Modesto, Primary Examiner 'Lewis (3on8v I Assistant Examiner-Richard L.Raymond [73] Assignee: Shell Oil Company, New York, N.Y. Att0rney-FrankR. La Fontaine and Marion W.

22 Filed: Dec. 31, 1969 western [21] Appl. No.: 889,705 [57] ABSTRACTImproved production of dimethyl l-methyl-2-(methyl- [52] US. Cl"260/969; 260/943 carbamoyl)vinyl phosphate by the reaction of 2- [51]Int. Cl. ...C07f 9/08 chloro-N-methylacetoacetamide with trimethyl phos-[58] Field of Search ..260/969, 943,990 phite, results from conductingthe reaction in the presence of a poly-halogenated lower alkane. [56]References Cited 4 Claims, No Drawings reaction system to be realized.

PROCESS FOR THE PRODUCTION OF DIMETHYL l-METHYL-2-(METHYLCARBAMOYL)VINYL PHOSPHATE BACKGROUND OF THE INVENTION This invention is animproved process for the production of dimethyl l-methyI-Z-(methylcar-,bamoyl)vinyl phosphate, the active ingredient of an insecticidemarketed commercially under the registered trademark AzodrinInsecticide.

DESCRIPTION OF THE PRIOR ART The reaction is carried out by adding thephosphite to the amide.

It has been disclosed in U.S. Pat. No. 2,802,855 that where the amide isa solid at ordinary temperatures, the use of an inert solvent such asxylene enables a fluid l. Alpha (a) lsomer (Methyl group cis to thecarbamoyl moiety) ll. Beta ([3) Isomer (methyl group trans to thecarbamoyl moiety) SUMMARY OF THE INVENTION This invention is an improvedprocess for the production of dimethyl 1-methyl-2-(methylcarbamoyl)vinylphosphate, which comprises reacting trimethyl phosphite with 2-chloro-N-methylacetoacetamide in the presence of a polyhalogenated lower alkanesolvent wherein each halogen has an atomic number from 17 to 35.

It has been discovered that when the phosphiteamide reaction is carriedout in the presence of one of these solvents, the purity, that is thepercentage of the alpha isomer in the insecticidal product, increases.This means that the same degree of insecticidal activity can be obtainedfrom a smaller amount of insecticide; thus, a higher quality insecticideis produced. Accompanying the purity increase is an improvement in yieldwhichincreases the quantity of the desired product obtained from thesame amount of reactants, thus decreasing intermediate materialconsumption. When incorporated into the existing process, this inventionenhances both the quality and quantity of the final product.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally polyhalogenated lowermolecular weight alkanes are suitable for this invention, for examplethose containing up to five carbon atoms and boiling between about 0 C.and 120 C. Specific examples would be methylene chloride, chloroform,1,1- and 1,2- dichloroethane', 1,1- and 1,2-dichloropropane, propylbromide and the like. Of these, the polychlorinated methanes arepreferred since they are inexpensive and readily available. Chloroformand methylene chloride are preferred. The process of this invention canbe conveniently incorporated into the normal procedure for theproduction of the vinyl phosphate. The amide. is a solid and thephosphite is a liquid at ambient temperatures, so for ease of handling,it is preferable to dissolve the amide in the solvent. Although theorder of addition is not critical, it is advantageous to add the amidesolution to the reaction vessel first to avoid the possibility ofphosphite reacting with contaminants which may be present in'thereaction vessel. The amide solution is added to a reaction vesselequipped with a stirrer, reflux condenser, addition facilities, atemperature indicator, and a heating-cooling system, the contents arebrought to-reaction temperature, and addition of the phosphite is thenbegun. Since the reaction is exothermic, the rate of mixing thereactants must be adjusted so the cooling capacity of the reactionvessel is not exceeded. Since the reaction is taking place in a solvent,the thermal effects are moderated. Upon completion of the addition ofthe second reactant, the reaction temperature is maintained until thereaction is completed. Although stoichiometrically only a l:l molarratio of phosphite to amide is needed for the reaction, to push thereaction to completion it is advantageous to have an excess ofphosphite. To avoid excessive recovery problems, it is best to have anex cess of no more than 100 molar percent phosphite, with 20 to 50 molarpercent being preferred. After the reaction is completed, the mass iscooled and the solvent and excess phosphite removed by distillation.

The temperature at which the process of the invention is carried out mayrange from as low as 20 C. or less up to C. or more with the pressurebeing atmospheric or the pressure attained during the reaction in arefluxing system. However, super atmospheric pressure may be used tomaintain the desired reaction temperature throughout the reaction. Thepreferred temperature range is about 55-65 C.

Since for ease of handling the amide is dissolved in the solvent, it isconvenient to relate the amount of solvent to the amide. The percentageof solvent incorporatedto improve purity and yield may range as low .as25 percent by weight or less to as high as 75 percent In order to pushthe reaction-to completion, it would be necessary to maintain aphosphite excess of no more than 100 molar percent, with a.20 to 50molar percent phosphite being preferred. .At the completion of thereaction the excess solvent andphosphite would be removed and finalproduct collected in a suitable vessel.

The following examples show the preparation of dimethyl1-methyl-2-(methylcarbamoyl)vinyl phosphate by batch and continuousmethods.

EXAMPLE I Batch Preparation of Dimethyl l-methyl-Z--(methylcarbamoyl)vinyl Phosphate without a Solvent Solid2-chloro-N-methylacetoacetamide (amide) was charged to a reaction vesselequipped with a stirrer, reflux condenser, addition funnel andtemperature indicator. The temperature was brought to 60 C. and heldconstant while enough trimethyl phosphite (TMP) was added over a 2-hourperiod to give TMP/amide mole ratio of 1.24. The reaction mixture wasthen held at 60 C. for additional2.5 hours at'the end of which time thereaction mass was cooled to room temperature. The reactor products werefirst stripped on a rotary evaporator at 75 C. and 1 Torr., then passedthrough a wiped-film evaporate (WFE) at 123 C. and 1 Torr. The bottomsproduct from each stripping was analyzed for dimethylI-methyI-Z-(methylcarbamoyl)vinyl phosphate. Results showed an 82.7percent m yield based on the amide and 81.7 percent w alpha isomer inthe final WFE product. Table 1, Example I, summarizes the operatingconditions and results.

EXAMPLE 11 Batch Preparation of Dimethyl l-methyl-2-(methylcarbamoyl)viny1 Phosphate in Chloroform Solution A 50 percentsolution of the amide in chloroform was charged" to the reaction vesselequipped as described in Example I. As on Example I, the temperaalphaisomer in the final product. Example 11 of Table 1 summarizes theseresults.

EXAMPLES III-IV Several runs were made following the same procedure asExample 11 with the chloroform content,

varying from'25 to 75 percent w. Table I, Examples 111 and IV,summarizes the results.

TABLE I Example No. I 11 111 IV Moles Amide Charged 1.05 1.00 1.00 1.00Moles TMP/Moles Y Amide (charged) 1.24 1.30 1.30 1.30 Cl-lCl, Dilution%w 0 50 25 75 TMP Addition T ime- Hrs. 2.0 2.0 2.0 2.0 Temperature "C 6060 60 Reaction Hold Timel-lrs. 2.5 6.5 6.5 18.5 Reaction Product Wtjgrams 286.4 419.2 313.0 739.3 Reaction Product a Residue low of totalreaction mixture 90.2 58.9 80.4 33.6 Product Purity, Off

Rotary Evaporator,

%w alpha isomer 72.2 77.4 75.7 76.0 Moles alpha beta isomers produced0.836 0.857 0.854 0.846 Moles Amide Reacted 1.011 .988 .988 .992 Yield,%m from amide 82.7 86.7 86.4 85.3 Moles TMP Consumed/Moles Amide 1.151.18 1.20 1.12 Purity-WFE'%w alpha isomer 81.7 84.5 83.2 83.1

EXAMPLE V Batch Preparation of Dimethyl l-methyl-2-(methylcarbamoyl)vinyl Phosphate in Methylene Chloride The amide wasadded to methylene chloride in a reaction vessel equipped with a refluxcondenser, tem-' TABLE II Example No. V

Moles Amide 0.1 Moles TMP/mole amide (charged) 1.3 Ml. solvent 25Reaction temperature (C) 53 Reaction time (l-lrs.) 4 Yield-%w 103 %walpha isomer in product. 85 Conversion of amide to alpha isomer-km I 881 Excess solvent, etc., was not removed completely giving overweightsamples and thus higher yields.

EXAMPLE Vl Preparation of Dimethyl 1-methyl-2- (methylcarbamoyl)vinylPhosphate in a 50 Percent Chloroform Solution. Four Stage ContinuousSystem A four-stage continuous stirred tank reactor system is employedconsisting of four reaction vessels, each equipped with a bottom drainvalve, agitating equipment, condenser, overhead chloroform trap,temperature indicator, and heating and cooling equipment. The firstreaction vessel was twice the capacity of each of the following threereactors. This particular design gave a residence time of about 7 hrs-.,which resulted in a mole percent conversion f the amide of more than 99percent. The volume of each reactor was level-controlled during thereaction while the TMP and the amide/chloroform solution were metered inat a specific rate. The temperature of the reaction vessels was held to63 C. throughout the course of the reaction. The reaction was run forabout 35 hours to allow the system to approximate a steady rate; thenthe reaction system was blocked out for four hours. At the conclusion ofthis period reaction feed weights, overhead weights, and product weightswere recorded and reactor samples taken. The results are summarized inTable III.

Reactor 2 82.9 Reactor 3 85.2 Reactor 4 88.2

Yield %m from amide Reactor 1 74.3

Reactor 2 79.4

Reactor 3 83.7

Reactor 4 87.7 TMP/Amide Molar Consumption Reactor 1 1.15

Reactor 2 LI? Reactor 3 1.22

Reactor 4 1.24 PURITY (OFF WFE) %w alpha isomer 84.9

The above experiments summarized in Table I indicate that a 50 percent wsolution of 2-chloro-N- methylacetoacetamide in chloroform offers thegreatest increase in the purity of the final product as well as the mostimproved yield. Increasing the percentage of chloroform to percent doesnot offer any further advantage in either yield or purity. v

As can be seen in Table 11!, running the reaction in the continuoussystem using a 50 percent chloroformamide solution indicates a similarincrease in purity and yield over the batch reaction run in theconventional manner.

I claim as my invention:

1. In the process for the production of dimethyl lmeth 1-2- methlcarbamo l vin l hos hate b the reaction of 'tri methyl p sphi te witli2-chlo ro-N- 3. The improvement of claim 1 wherein the polychlorinatedmethane is chloroform.

4. The improvement of claim 2 wherein the reaction is carried out in acontinuous system.

2. The improvement of claim 1 wherein the polychlorinated methane ismethylene chloride.
 3. The improvement of claim 1 wherein thepolychlorinated methane is chloroform.
 4. The improvement of claim 2wherein the reaction is carried out in a continuous system.